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Do Diets Work?

Did you resolve to lose weight this New Year? If so, you are not alone. “Lose weight” is the #1 New Year’s resolution for 2014. Many people link weight loss with health improvements. In fact, “Stay fit and healthy” is the #5 most popular resolution. These resolutions are supported by the weight loss industry, which has a financial interest in “helping” you make weight loss resolutions. In January we are bombarded with advertisements for diet plans and various weight loss methods. In addition to the media, people who are overweight or obese are often encouraged by their physicians to lose weight through dieting as a means of improving health. Given the emphasis on weight loss for health improvements, I think that it is important to ask: does losing weight actually lead to long-term health benefits?

Recently, a group of researchers tackled this question. In “Long-Term Effects of Dieting: Is Weight Loss Related to Health?” Tomiyama, Ahlstrom, and Mann (2013) explored the relationship between dieting, weight loss, and health outcomes. The researchers reviewed 21 previously published randomized controlled trials that examined weight loss diets with a follow-up period of at least 2 years. They investigated health outcomes including total cholesterol, triglycerides, systolic and diastolic blood pressure, and fasting blood glucose.

The researchers found that participants in the dieting conditions lost an average of 2 pounds from starting the diet to follow-up. This was about 3 pounds more weight loss than the control condition. In addition to weight loss, the dieting groups experienced some minor health improvements, many of which would not be considered clinically significant. These health improvements are described below.

The dieters experienced a reduction in blood pressure of 2.37 mmHg for systolic and 2.71 mmHg for diastolic. This was 2.21 mmHg lower for systolic blood pressure and 0.50 mmHg lower for diastolic blood pressure than the control group.In terms of fasting blood glucose (a test used to diagnose diabetes), participants in the dieting conditions averaged a decrease of 0.05 mmol/L. Two large studies reviewed reported on the incidence of diabetes. Both reported that diabetes was significantly reduced by 58% in the dieting group when compared to a control group. Tomiyama et al. note that both of these studies included exercise in the diet group but not the control group, making it difficult to know whether diet or exercise was responsible for the reduced incidence of diabetes in the dieting groups. Participants in the dieting groups experienced small decreases in both cholesterol and triglyceride levels. Diets did not lead to any significant reductions in coronary morbidity or mortality.

The researchers then asked, were these health improvements related to weight loss? Their conclusion was NO. The authors’ analyses indicate that any health improvements that were found in the dieting groups were not related to weight loss. Some possible explanations for the improvements that the authors pose are exercise, changes in nutritional intake (ie. increased fruits and vegetables, increased fiber, decreased sodium), differences in medical care, and social support.

So, while dieting may lead to some minimal improvements in health (many of which would not be considered clinically meaningful), these improvements are not related to weight loss. Again, it turns out that weight is not the key factor underlying health.

If you are one of the millions of Americans who will make a New Year’s Resolution today, consider “staying fit and healthy” rather than “lose weight.” Remember that the two are NOT the same! We can improve our health independent of weight loss and healthy bodies come in a diverse range of shapes and sizes. For 2014, resolve NOT to diet! Join the growing movement against dieting and sign the No Dieting Pledge here.

I believe that people should do intermittent fasting (with some exceptions of course). This is NOT a diet. Rather, this is changing the window of time that a person eats. So a 16:8 intermittent fast consists of a 16 hour fast and an 8 hour eating window. An example would be when a person eats between 10 AM and 6 PM and fasts until 10 AM the next day.

The caption and the author's conclusions suggest that the article is about the connection between weight loss and health outcomes ("....is weight loss really the key factor underlying health improvements?"). Yet the participants only lost an average of 2 pounds? What conclusions about the benefits of weight loss can be drawn from that?

If you look at real studies of true weight loss, especially in the context of people who are obese, you will come to a different conclusion. People who really do need to loose weight generally experience significant health benefits after loosing weight. They just have a hard time doing it. It is not responsible to suggest that they won't receive health benefits and to discourage them from doing what is already difficult, but that could help them greatly.

It is notable that participants who dieted only lost about 2 pounds at 2 year+ follow-up! Remember that this is pooled data from 21 previously published studies. In my mind, this indicates that dieting is neither effective for weight loss nor clinically significant health outcomes. The study did show that the minor health improvements experienced by the dieters was not related to weight loss. I agree that it would be interesting to look at long term studies of "true weight loss." The only problem is that these studies are hard to find- because it is nearly impossible for people, especially those who are obese, to lose and maintain significant amounts of weight. In fact, this phenomenon is so rare that there is a national registry for those few usual specimens who have been able to accomplish this feat. More often than not people who diet end up weight cycling ("yo-yo") which research shows is not good for our health. My point is that people can improve their health independent of weight loss. I encourage people to focus on health improvements rather than weight loss. This is a far more attainable and less discouraging goal.

"Yet the participants only lost an average of 2 pounds? What conclusions about the benefits of weight loss can be drawn from that?"

Precisely. The participants only lost an average of 2 pounds. Yup. That's one of the main points of that study: diets do NOT lead to long-term significant weight loss. They just don't. 2 pounds: that's what you can hope for in the long term when you put someone on a diet, no matter what.

Except they don't lose the weight for long. In a couple of years, it's all back - and more, quite often - and they are in a worse situation health-wise than they were to begin with.

"They just have a hard time doing it."

Not hard: nearly impossible. Think about it: smokers and alcoholics have a hell of a hard time stopping a single habit. All they have to do is STOP doing ONE clearly defined thing - and yet they struggle horribly about it. Obese people have it even harder, because they cannot just stop eating. They have to keep eating, but in an extremely controlled way, for the entire rest of their life. That's like asking a smoker to smoke exactly 5 cigarettes, or an alcoholic to drink exactly 3 glasses, at exact times of the day, no matter the circumstances, all year long, and with a punishment if they don't keep to that strict rhythm. This is beyond hard to achieve: it's sadistic. And yet, that's exactly what is expected of obese people. Uh-huh. Totally gonna happen.

"It is not responsible to suggest that they won't receive health benefits and to discourage them from doing what is already difficult, but that could help them greatly."

Actually, it's the exact opposite: being obese but at a stable weight is less dangerous than dieting - because dieting inevitably leads to yo-yo dieting, which is MUCH worse than just obesity. So it's encouraging people to "just lose weight already" which is irresponsible, since it puts them in an even greater danger health-wise than their weight does. Focusing on physical activity ONLY is the right way to go, because it's the only thing that's been proven to make a real difference.

Cardiologists are tasked with fixing people's heart. Losing weight if the person is obese would help their heart. Thus, it's perfectly logical that cardiologists would recommend obese people lose weight.

But cardiologists are utterly USELESS when it comes to HOW people are supposed to lose that weight. They don't know how to achieve that any more than anybody else.

And it shows since this metastudy proves that people just do NOT keep the weight off, no matter what diet they used.

"their decades of disgusting self-indulgence at the dinner table"

Self-indulgence? What kind of self-indulgence is it that makes people miserable?? Self-indulgence is supposed to make someone happier. Being obese makes most obese people miserable. So it can't be self-indulgence that got them there, by definition.

One thing I heard from a health professional that has stuck with me -- You don't see elderly obese people. They die young. It's unhealthy to be obese. Overweight, not as much. But watch out for type 2 diabetes if you're overweight. It will shorten your life.

Do you know who dies MUCH younger than obese people? People who develop anorexia or bulimia.

Bulimia (the type where you make yourself throw up regularly) can kill you in a matter of months if you're not lucky. That would be short term.

Anorexia maintained over years will kill you in the middle term.

Obesity will kill you on the long term.

So where is the logic in encouraging absolute self-control (of which anorexia is one type) or weight loss at any price (of which bulimia is one type) when those are MORE likely to kill you SOONER than the original problem itself?